Glass composition



Nov. 23, 1948. v

c. E. LEBERKNEGHT ET AL 2,454,607

GLAiS COMPOSITION Filed Mg. 19, 1946 CEN T/GRADE DEGREES INVENTORS 6J2 arias .E'Leb erkmgght Ei gene C. 0s trander 4 4M 29. 91%

Patented Nov. 23, 1948 GLASS COMPOSITION Charles E. Leberknight and Eugene C. Ostrander, Edgewood, Pa., assignors to Kopp Glass, Inc., Swissvale, Pittsburgh, Pa., a corporation of Pennsylvania Application August 19, 1946, Serial No. 691,470

2 Claims. 1

This invention relates to a glass composition for glass-to-metal seals and particularly to a glass composition for making such seals with an iron-nickel alloy nominally and approximately composed of 42% nickel and 58% iron which is characterized by a sharp break in its cooling or expansion curve in the neighborhood of 400 C., and to seals so made.

In providing a glass for sealing to this specific alloy and slight variants thereof it has been desired to obtain and use for such purpose a lead-free glass, because of the tendency of a leadcontaining glass to plate out against the metal in making the seal. It is, however, essential in so doing that the sealin properties and physical characteristics of the glass be suitable for forming the seal and in use of the seal when made.

It is essential in making good glass-to-metal seals that the glass and metal have the same total contraction in cooling from the setting I temperature of the glass to room temperature. It is highly desirable that in cooling through that range the rate of contraction of the glass and the metal should be nearly equal at all temperatures during their cooling, and it is particularly desirable that the coefiicients of expansion of the glass and metal should be approximately identical in the lower portion of the cooling range. These requirements have been met previously in lead-free glasses having a very high content of B203, but an undesirable characteristic attendant upon such high inclusion of B203 is a lack of good weathering properties.

We have discovered a glass which meets the above requirements in its expansion characteristlcs with respect to the expansion characteristics of the above noted iron-nickel alloy, and which has good weathering properties.

An analysis of such glass taken from the batch composition falls within the following ranges:

Table A B203 20% to 24% A1203 3% to 6% T102 2% to ZrOz .5% to 1.5% NazO Not less than 2% of each of these K20 alkali metal oxides L120 7% to 12% S: 56% to 68% The foregoing ranges allow for adjustment for variation in the composition of the said 42% nickel-58% iron alloy, examples of which in some measure vary in their expansion characteristics.

As shown, the curves for the said iron-nickel alloy and glass are plotted in accordance with the standard procedure taken at the cooling rate of 1 centigrade degree per minute. The glass from which the curve designated G is taken, is calculated from the batch and has the approximate composition:

Table B Per cent B203 22 A1203 5 TiOz 3 ZrOz 1 S102 58 NazO 5 K20 3 L 3 It will be noted from the plotting of the curves that the total contraction of the typical example of the said iron-nickel alloy as represented by the curve M and the total contraction of the glass as denoted by the curve G are equal from the setting temperature A of approximately 480 C. down to room temperature. Also it will be noticed that throughout the entire cooling range these curves do not separate at any temperature Widely enough to break the seal. At the lower temperature end of the cooling range, from about 200 C. downward, the curves are approximately coincident. Substantial equality in the expansion characteristics of the glass and metal at temperatures up to about 200 C. assures that the seal when once formed will not be broken by subsequent reasonable elevation in temperature which the seal may incur in service.

It may be noted that in the specified composition the TiOz serves not only to perform the expension-controlling function which would be performed by an increased proportion of B203, but that it and the ZrOz perform a positive function in improving the weathering properties of the glass.

2,454,607 3 4 We claim as our invention: 1. A metal sealing glass consisting of 20% to REFERENCES CITED The following references are of record in the 24% B203; 3% to 6% A1203; 2% to 5% T1022 .5% to 1.5% Z102; the sum of NazO, K20 and fi Of th s pate t:

LizO; 7% to 12% with not less than 2% of each of these alkali metal oxides; and 56% to 68% 5 UNITED STATES PATENTS S102; calculated from the batch composition. Number Name Date 2. A metal sealing glass consisting in approxi- 1,394,296 Fisher Oct. 18, 1921 mate relative proportions of 22% B202; 5% A1203; 1,557,540 Horak Oct, 13, 1925 3% TiOz; 1% ZrOz; 58% S102; 5% NazO; 3% 1O K20; and 3% LizO; as calculated from the batch composition.

CHARLES E. LEBERKNIGHT. EUGENE C. OSTRANDER. 

